Has any other teachers felt this way when they first began to teach?

I am currently student teaching a first grade class;however, when I am finished I am EXHAUSTED. I am mentally and physically exhausted. Has anyone felt this tired afterwards? Is this job always this draining or is because I am new? I also want to ask did anyone feel like some of the questions the students ask you second guess yourself if you are right? I know I am not a stupid person with a gpa almost a 4.0 but why am I having a hard time here? The students will sometimes ask me questions (simple questions) and It has been so long since I went to the core foundation of education that I am having a hard time. I have a lot of anxiety so I dont know if that has something to do with it. I have wanted to teach my entire life and I have never second guessed it. I am not second guessing that I want to teach because 100% I do. I am second guessing me being able to actually teach them! My friend who is also a student teacher thinks I am over analyzing every question they ask me. Any advice? Did you also feel this way ?